A method of measuring the three dimensions of a point on a surface based on the time of flight of light as disclosed in U.S. Pat. No. 4,199,253. Shuttering of the received light, such as could be obtained by gating a micro-channel plate on and off, enabled the identification of the time required for a light pulse to travel to the surface, reflect for the surface, and travel to the receiver. It was shown how a single light pulse with multiple receivers in parallel could make this measurement. And it was shown how a single receiver with multiple light pulses could make this measurement.
Optical gating components with the requisite switching speed (light travels round trip in about 2 nano-seconds to a target 1 foot away) have been costly and require relatively high switching voltages. Also, needed components are not available at all frequencies. For example, at 10.mu. meter wavelengths, microchannel plate amplifiers are not available to provide the gating function. It is therefore desirable to provide the same measurement capability without the need for such components.